Re: Changing rings and piston on a 1990 Mariner 60 with no head
You can semi check the pistons through the exhaust port by removing the exhaust plate and baffle. This will allow you to turn the engine and inspect a portion of the pistons. Any water intrusion will be seen from there. The piston that usually takes the hit is number three (BOTTOM PISTON). Corrosion from water intrusion will in time cause the piston to decintegrate and particals from the piston will be ground up and obviously be on the plugs and will enter the case and settle at the bottom end cap. Becuase the cylinder walls are steel there may be a chance the cylinder is re workable with honing , Boring and a new piston, wrist pin, needle bearings, etc etc. <Tear down> Getting the nuts off the studs holding the power head on may be a dificult task esspecailly if the nuts are corroded and rounded. The method i use to remove these would be to take a smal wood chisel and make an indent just off center of the nut (Left side) deep enough to grab the meat of the nut so that when you strike it with a hammer it will not take the meat off the nut but in fact move the nut (Counter clockwise) in the direction to take it off. This process must be continued on every flat of the nut all the way around the nut until the nut is removable. Plenty of soaking with PB Blaster is reccomended. Get new stainless steel nuts if a re assemble is eminent with SS washers. After removing all the nuts knock the roll pin out of the shifter lever and remove it. (LU Removal suggested and then the shift shaft from the lever). The carbs, airbox, starter, etc etc must be taken off as well as all the electrical. Take pictures of all angles to assist you in re installing if eminant after inspection and the rebuild. Many blots such as the exhaust cover, rear jacket cover may be corroded and again soaking is reccomended. When I did my 2 engines I found that the most effective way was to get the bolt to slightly move in the counter clockwise direction then turn back in the clockwise direction just a bit at a time to start to free the bolt and repeat this process constantly no mater how long and irritating it becomes. Many breaks may be needed as this is a time consuming process and a whole lot of patience is required to have success. If you do this the rate of success I had was 98 %. I guess you cant win them all all the time. After removing the PWR HD, Remove the covers for inspection for corrosion cracks etc. Un do the endcaps and unbolt the intake case. Do a visual of the componants before disasembling it to determine the amount of play. First from the rods and the center bearings the outter bearings can be checked after the crank is removed and then check for a wiped journal. After removing the crank check the side to side play of the connecting rods to determin if the wrist pins, and rods are in good condition or need attention. At that point remove the pistons and check the cylinder walls for scoring or pitting. That should also give indication of the piston condition. Mic the cylinder to see if it needs boring to an oversize etc etc. if all looks good then a good cleaning of the block and possible resurfacing of the side and the rear may have to be undertaken to get the covers to seal properly. Check the area around the plugs for corrosion as this is the main spot that gets hit the worst. I had mine heli arch welded and then flled it down and it seems fine. I,m still finnishing mine up and everything looks good eccept for a slight intermintent miss when idleing and increasing throttle but nothing serious may be plug or wire related if not just leftover cabon on one of the pistons fouling a plug. I didn,t clean one very well. Sea foam to the rescue. Good luck
